Integrated circuits, in particular, integrated memories, for example, in the form of  DRAMs (Dynamic Random Access Memory), are generally subject to extensive functional tests in the fabrication process. These functional tests are used, inter alia, to identify defective circuit sections, such as defective memory cells, defective bit lines, or defective word lines. As memory size increases, the costs of functional tests take up an ever larger proportion of the total production costs of a memory. In order to lower the test costs, there is increasing use of special techniques, for example, additional test logic implemented as a BIST (Built-In Self-Test) unit.
For repairing defective memory cells, integrated memories generally have redundant memory cells, which are usually combined to form redundant word lines or redundant bit lines, which can replace, in address terms, regular lines having defective memory cells. As a result, integrated memories, in particular, DRAMs, can still be fabricated economically in the context of the integration densities achieved nowadays. A memory is tested by an external test device, for example, and redundant elements are subsequently programmed based on a redundancy analysis. In this case, the addresses of those memory cells which have been tested and have been detected as being defective, are stored in a defect address memory in order, in a subsequent step, to replace these memory cells by defect-free redundant memory cells based on the stored addresses. Alternatively, a memory test of this type may be implemented in an analogous manner by a self-repair circuit (BIST unit) of the memory for implementing self-test and self-repair operation for checking the functioning of, and repairing, defective memory cells of the memory.
Even though intensive testing, repair and selection are usually effected at the wafer and component level, it is often the case that, after tested integrated memories have been applied to, in particular, soldered onto, a module substrate, memory cells fail, for example, on account of the thermal loading in the soldering step. This can give rise to costly subsequent repairs or may even mean the complete loss of the module.